1. Field of the Invention
The present invention relates to a method and an apparatus for producing an electrophotographic blade member such as a cleaning blade and a developer amount regulating blade used in an image forming apparatus, such as an electrophotographic copier, a laser beam printer, and a facsimile, utilizing an electrophotographic process.
2. Description of the Related Art
Conventionally, as a developing apparatus in an image forming step of an electrophotographic apparatus such as an electrophotographic copier, a laser beam printer, and a facsimile, there has been widely used one including a developer carrier and a developer amount regulating blade. The developer carrier, such as a roller, is provided to be partially exposed at an opening portion of a developer container containing developer (toner), and the developer amount regulating blade includes an electrophotographic blade member which is made of a rubber material or the like and is brought into contact with the surface of the developer carrier. Further, as a cleaning device in a photosensitive body cleaning step of the electrophotographic apparatus, there has been widely used a cleaning blade in which the electrophotographic blade member is joined to a support body in order to remove residual toner on the photosensitive body and repeatedly perform transferring after performing transferring on a recording sheet.
The developer amount regulating blades are generally formed of a rubber plate, a metal thin plate, a resin plate, and a laminated body formed of those plates. The kinds of the developer amount regulating blades are selected depending on developer to be used. As one of the generally-used developer amount regulating blades, there may be given one including an electrophotographic blade member which is brought into press contact with the developer carrier, and a supporting member for supporting the electrophotographic blade member at a predetermined position. For the electrophotographic blade member, a polyurethane resin is usually used because it is excellent in mechanical characteristics such as abrasive resistance.
The cleaning blade includes a metal supporting member for bonding the blade to the apparatus or the like, and an electrophotographic blade member which is formed of an elastic body and formed integrally with the supporting member. For the electrophotographic blade member, the polyurethane resin is usually used because it is excellent in abrasive resistance and permanent deformation.
The above-mentioned electrophotographic blade including the electrophotographic blade member made of the polyurethane resin is conventionally produced by any one of the following production methods.
One production method is called a centrifugal molding method. In the centrifugal molding method, a raw material is put in a cylindrical die to be rotated at high speed, and then is infilled on an inner peripheral surface by the centrifugal force to be subjected to thermosetting, to thereby mold a thin cylindrical sheet. The cylindrical sheet thus obtained is released from the cylindrical die, subjected to secondary crosslinking as needed, and then cut into a predetermined dimension. Thus, the electrophotographic blade member is produced. Then, by bonding one side edge portion of the electrophotographic blade member to the supporting member by an adhesive or the like, the cleaning blade and the developer amount regulating blade are completed as finished products.
Another production method is called a die molding method. In the die molding method, the supporting member on which the adhesive or the like is applied in advance is set in split dies, and the raw material is injected into the split dies to be subjected to thermosetting, to thereby integrally mold the supporting member and the electrophotographic blade member. After that, the split dies are opened, and the molded product is taken out. In order to ensure edge (edge line) accuracy, one side surface side of the molded product may be sometimes cut after the molding.
Those methods leave room for improvement in terms of the following points. First, the centrifugal molding method performs batch processing, which is difficult to realize continuous automation. Further, the die molding method requires preparation of a large number of dies for mass production, and also requires a curing oven. As a result, the size of the entire apparatus is increased, which leads to an increase in space to be ensured and apparatus cost.
As a conventional method for molding a polyurethane sheet continuously, the following method is provided. Specifically, a liquid of polyurethane prepolymer as a raw material component of thermosetting polyurethane and a liquid of a crosslinking agent are mixed and stirred to be discharged into the heated die having the continuous recessed sectional shape, and then are heated and pressurized, to thereby continuously mold the electrophotographic blade member having a constant width and a belt-like shape. In this technology, it is possible to continuously mold the electrophotographic blade member, and facilitate and simplify automation of a producing step. In addition, it is possible to reduce facility cost.
In recent years, also in the technical field of electrophotography, cost competition is being increased, and a production method with improved productivity is demanded to reduce cost. For the electrophotographic blade member using the polyurethane resin, an improvement of production efficiency, which is realized by making the curing time shorter, and downsizing of the apparatus are demanded.
However, in a case of using the raw material composition of the polyurethane resin which is formed of the polyurethane composition with the short curing time, when injected into a groove with a recessed sectional shape of a heated molding drum, the composition starts to cure directly after being brought into contact with the molding drum. Thus, the curing progresses from the surface that is held in contact with the molding drum, and a difference is made in curing timing between the surface held in contact with the molding drum and a surface that is thereafter brought into contact with the endless belt. Consequently, irregular curing occurs. As a result, there is a fear that, due to occurrence of marks in appearance such as sink, intrusion of air bubbles, and the like, provided is a molded product that cannot satisfy the function as the electrophotographic blade member.
Further, in a case of using the raw material composition of the polyurethane resin formed of the polyurethane composition with the short curing time, and injecting the composition into the groove with the recessed sectional shape of the heated molding drum, the curing progresses before the composition is sandwiched by the endless belt. Thus, there is a fear that a predetermined thickness cannot be obtained even when the raw material composition of the polyurethane resin, in which the curing has progressed, is sandwiched by the endless belt (for example, see Japanese Patent No. 2645980).
Further, as another conventional method for continuously molding a sheet using the polyurethane resin, the following is given. Specifically, as the apparatus for continuously molding the sheet by the molding drum and the endless belt, the molding drum having a molding surface formed over an entire periphery of the outer peripheral surface, the endless belt being brought into press contact with a part of the outer peripheral surface of the molding drum, there is described a thermosetting elastomer continuous molding apparatus, in which pressurizing is performed by a back pressure roll from the back surface of the endless belt. In this technology, continuous pressurizing is performed and a pressurizing force is large, and hence the continuos molding apparatus involving no pressure nonuniformity can be provided, with the result that intrusion of air bubbles into the molded product can be prevented.
In this method, the back pressure roll is provided on the back surface of the endless belt, and intrusion of air bubbles is prevented by high load tension of the endless belt, with the result that the configuration of the apparatus is complex. Thus, an increase in size of the apparatus, an increase in cost of the apparatus, and complexity of setting and adjusting of the apparatus are problems to be solved (for example, see Japanese Patent Application Laid-Open No. H10-15967).